Due to the recent growing consciousness of energy-saving, there has been a demand for reducing the electric energy consumption as much as possible when various types of industrial machines perform positioning control using a motor, such as a servo motor.
Thus, inventions of Patent Documents 1 to 7 are published as methods for thus reducing electric energy consumption during positioning control.
Patent Document 1 discloses a head positioning apparatus which aims to reduce electric energy consumption according to a user's use, and to efficiently perform positioning control regardless of changes in temperature, deterioration over time, etc. A velocity profile store unit stores target velocity profiles A and B in advance, the target velocity profile A supporting high-speed seek, and the target velocity profile B supporting low-speed seek with low electric energy consumption, such that the user can select the profile A or B. A subtracter compares a current track position of a head with a target position to produce a position error signal. A target velocity setting unit outputs a target velocity of the head, based on the position error signal, and based on the target velocity profile A or B in the velocity profile store unit. A control unit calculates a drive current for a head driving motor, based on a velocity error signal and servo control constants. The calculated drive current is inputted to a motor driving unit. A drive current initial value store unit stores an initial value of the drive current. A comparator compares the current drive current with the initial value. A servo control constant adjusting unit adjusts the servo control constants of the control unit, based on the result of the comparison made by the comparator. Both the target velocity profiles A and B have a triangular shape. In particular, the target velocity profile B reduces electric energy consumption by increasing the seek time instead of reducing the seek velocity.
Patent Document 2 discloses a method for thermal optimization, which aims to obtain a method for optimizing the movement performance of a robot with respect to the electric power loss in the driving system of the robot. The method of Patent Document 2 is a method for optimizing the movement performance of an industrial robot for a current movement path with respect to electric power losses in the driving system of the robot. The method includes the steps of calculating the electric power losses for the whole or part of the movement path for at least one component in the system, comparing the calculated electric power losses with a maximally allowed electric power loss for the component, and depending on the comparison, adjusting a course of accelerations and velocities for the current movement path.
Patent Document 3 discloses a method for generating command pattern, which aims to generate a command pattern that minimizes the temperature rise of a drive motor, when an amount of movement and a tact are specified. According to the method of Patent Document 3, by determining two of four parameters, i.e., an amount of movement θmax, a tact “tact”, a maximum velocity ωmax, and a maximum acceleration αmax, the two parameters including at least the maximum velocity ωmax or the maximum acceleration αmax, then the amount of movement θmax and a tact “tact” are determined, and a parabolic velocity command pattern is generated, which has the velocity of 0 at time 0 and at time tact, and has an area equal to the amount of movement θmax. The velocity command pattern is parabolically shaped to minimize copper losses.
Patent Document 4 discloses a control apparatus for a machine tool, which aims to optimally reduce the overall electric energy consumption of the machine tool. The apparatus of Patent Document 4 is provided with: first electric energy consumption calculation means for calculating the electric energy consumption of a feed shaft driving motor; second electric energy consumption calculation means for calculating the electric energy consumption of a device that operates at constant electric power; and motor control means for determining a time constant relatively related to at least one of the accelerating time and decelerating time of the feed shaft driving motor, and controlling the feed shaft driving motor based on the time constant, the time constant being determined based on the sum of the electric energy calculated by the first electric energy consumption calculation means and the electric energy calculated by the second electric energy consumption calculation means. The time constant is determined so as to minimize the sum of the electric powers.
Patent Document 5 discloses a trajectory generating apparatus capable of reducing required energy. The trajectory generating apparatus of Patent Document 5 generates a trajectory through interpolation of a sequence of points with a clothoid curve. The trajectory generation apparatus is provided with an arithmetic processing unit having clothoid curve generating means. The clothoid curve is a triple-clothoid curve, thus ensuring continuity in tangential direction and continuity in curvature at a point through which the curve passes. In the case that its end point is connected to a straight line, its tangential direction is made identical to a direction of the straight line.
Patent Document 6 discloses a control apparatus for a robot, which aims to reduce energy consumption during PTP (point to point) operation, without increasing operating time. The apparatus of Patent Document 6 determines, in control of a multi-axis motor with a common bus, a moment at which each axis command operation starts, such that decelerating operations of a plurality of axes do not overlap each other. The apparatus prevents regenerative energy from increasing as a result of the decelerating operations overlapping each other, and prevents the regenerative energy from being consumed by a regenerative resistor.
Patent Document 7 also discloses a control apparatus for a robot, which aims to reduce energy consumption during PTP operation, without increasing operating time. The apparatus of Patent Document 7 computes, in control of a multi-axis motor, the operating times of a plurality of axes, and increases command times for shorter operating times in accordance with the longest operating time, thus reducing the electric energy consumption.